Solar Panel Fire A Guide to Arc Faults. 

Can solar panels start a fire? This is a common concern we receive from our clients who are thinking about going solar. The short answer is yes but so may your dryer, toaster, or even an ordinary socket. A solar array can produce a massive amount of electricity, and where there is electricity, there is always a chance of fire. 

So how are electrical fires started and how is the risk minimized? Electrical fires are started when an arc fault ignites surrounding flammable materials. An arc fault is an unplanned, unintentional path of electric current that “arcs” and superheats anything in its path. This may be due to improper wiring, or exposed and/or damaged wire insulation which is the protective sheathing that covers the bare metal wire inside.

Thankfully, modern Photovoltaic architecture, electrical codes, and inspectors work together to prevent fires from PV arrays in any event. PV wires are typically joined by MC4 connectors which can only be connected when installed correctly and make an audible snap when secured together properly. This allows installers to know they’ve made proper connections and that there is no chance of an arc fault. In some cases, wire nuts are used instead of MC4 connectors to terminate loose ends, and strict measures are taken to ensure the current cannot continue. The insulation wrapped around any wires used in solar energy production is also designed to reduce the possibility of arc faults. These wires are heavily insulated and made to be tough as nails in order to withstand decades of exposure to direct sunlight and inclement weather. However, there is still a risk of bad connections, poor terminations, or rodents chewing through the insulation resulting in dangerous arc faults. 

If terminations were not made or improperly made there would be a much greater risk. For example, in some cases such as an Enphase installation, there will be one loose end at the end of any series of panels that are strung together. Enphase uses microinverters that sit behind each panel converting DC to AC, decentralizing the point of conversion. Therefore, unlike SolarEdge which has a central point of conversion, the positive and negative wires are insulated, then reinsulated together in one wire. To safely terminate these wires, we have to cut open the external insulation, and cap both the positive and negative wires separately with wire nuts to ensure the current has nowhere to go.

Even if rodents chew through your PV wire, bad connections are made, and loose ends aren’t terminated, the inverter will protect your house and system. Inverters, which are an intelligent component of a PV system that convert the DC power from solar panels to AC power you use in your home, have mechanisms that can detect any arc fault. These inverters continuously monitor your system and will cut power within 1/12 of a second of it detecting an arc fault. 

Finally, Inspectors check our work and ensure everything is to code before activating the system. Every facet of solar design with these precautions in mind. All the safety measures and mechanisms in place today make solar panels effectively less dangerous than your toaster.